Dynamic Changes in pStat3 Are Involved in Meiotic Spindle Assembly in Mouse Oocytes

Abstract

The signal transducer and activator of transcription 3 (Stat3) is activated upon phosphorylation at Y705 (pStat3) and serves the dual function of signal transduction and transcription activation. Our previous study suggested that pStat3 is functional during oocyte maturation when transcription is silenced. Therefore, we speculated that pStat3 serves other functions. Immunocytochemical analysis revealed that pStat3 emerges at microtubule asters and spindle and is subsequently localized at the spindle poles along with pericentrin during mouse oocyte maturation. Both Stat3 and pStat3 proteins were detected in conditionally knocked out Stat3−/− mouse oocytes. pStat3 localization was the same in Stat3+/+ and Stat3−/− oocytes, and oocyte maturation proceeded normally, suggesting that pStat3 was still functional. Furthermore, the treatment of oocytes with the Stat3-specific inhibitors stattic and BP-1-102 or anti-pStat3 antibody led to significantly abnormal spindle assembly and chromosome mislocation in a dose-dependent manner, and pStat3 was either absent or improperly localized in these oocytes. Moreover, the development of pre-implantation stage embryos derived from inhibitor-treated oocytes was significantly hampered following in vitro fertilization. These findings indicate a novel function of pStat3 in spindle assembly.

STAT3 Is an Upstream Regulator of Granzyme G in the Maternal-To-Zygotic Transition of Mouse Embryos

“…The Stat3 -deleted oocytes showed normal maturation, fertilization and preimplantation development [ 65 ]. The current study also showed that the oogenesis was normal when maternal Stat3 was deleted at the primordial follicular stage in Stat3 f / f ( f /−) ; Gdf9 - iCre female mice [ 66 ]. Therefore, STAT3 may be expressed before the primordial follicular stages or have other origins, such as cumulus cells [ 67 , 68 ].…”

“…In addition, STAT3 inhibitors, Stattic and BP-1-102 were used to analyze the correlation between STAT3 phosphorylation and oocyte maturation. Interestingly, Y705-pSTAT3 plays a novel role of spindle assembly at oocyte maturation [ 66 ]. Those reports indicate that STAT3 plays multiple roles at oogenesis and preimplantation development.…”

“…In the zygote and two-cell embryo stages, STAT3 may interact with the spindle assembly in our inhibitor assay. Nevertheless, Y705-pSTAT3 was not detectable from germinal vesicle breakdown (GVBD) to early two-cell stage embryos [ 34 , 66 ]. STAT3 is not possible to play the role of spindle assembly by Y705 phosphorylation.…”

Electroporation‐mediated genome editing in vitrified/warmed porcine zygotes obtained in vitro

“…The samples were washed and then incubated with Alexa Fluor 488‐anti‐rabbit secondary antibody (1:300, A‐11070, TFS) for OCT4, or Alexa Fluor 488‐anti‐mouse secondary antibody (1:300, A‐11070, TFS) for CD46 at room temperature for 1 h. As a negative control, we reacted the samples with the secondary antibody alone. The samples were transferred onto a glass with SlowFade Diamond Antifade Mountant with DAPI (S36968, TFS) and imaged using a Zeiss LSM780 confocal microscope (Haraguchi et al, 2020).…”